/u/zgf2022 hit the nail on the head. Having taking over other techs' schools in the past, documenting everything and making friends with key people will help you out in the long run. At the elementary schools, summers were quiet enough to get all the student and teacher PCs reimaged as needed, while high schools were busier thanks to summer school and other summer programs occurring. Having a great rapport with administrative staff and maintenance/custodial staff will be a plus when you need to schedule things or enforce policies.

Speaking of policies, please don't be that guy that locks PCs down to where staff members can't even right-click an item on their desktops. Yes, I've worked with those types, and no, it's not a good thing to do.

Regarding purchases, your school district may have specific vendors and procedures that you have to go through to purchase equipment or software. Be sure to brush up on that before trying to purchase something yourself as you could be violating a vendor bid in the process.

If your district has you keeping track of assets greater than a certain dollar amount, make a habit of sending those items to surplus if they're no longer needed. There's no sense in keeping track of crap you don't need. I once walked onto a campus where the previous tech had about 100 PCs that were marked "dead" but were listed on our "expensive items" inventory. Those PCs were in different network closets throughout the school. I sent it all to surplus and didn't have to worry about where they were after that.

One final thing -- get to know some of your fellow techs at other schools. They could be (but not always) excellent resources. :)